17 Mar Understanding Addiction as a Brain Disease
Scientists and mainstream society often have differing points of view on key medical issues, including the nature of substance abuse and addiction. In some corners of society, abuse and addiction are viewed as moral, intellectual, or emotional failings on the part of the affected individual. However, over roughly the past 20 years, doctors and researchers have developed another view of abuse and addiction that centers on long-term, substance-driven changes in normal brain chemistry and brain function. Evidence for this point of view is so strong that scientists in the field commonly refer to addiction as a chronic brain disease.
Basic Brain Function
On a basic level, the human brain is a collection of nerve cells (neurons), each of which relies on electrical impulses for its internal function and chemical interactions for its ability to communicate externally with others of its kind. The chemicals that neurons use to communicate with each other are called neurotransmitters; when released by a nerve cell, these chemicals achieve their effects by traveling to an adjacent neuron and binding to attachment points on the target cell called receptors. In response to the presence of neurotransmitters on its receptors, a neuron can increase its electrical activity (grow more excited), reduce its electrical activity (become less excited), or maintain its current level of activity. Generally speaking, excited neurons support continuing cell-to-cell communication by releasing their own neurotransmitters, while unexcited (or inhibited) neurons reduce the likelihood of continued communication.
Your brain relies on different neurotransmitters for different effects. For example, a neurotransmitting chemical called serotonin helps control fluctuations in your emotional state. Another neurotransmitter called dopamine helps activate your limbic system, which is an area of your brain responsible for rewarding certain actions with an increase in pleasurable sensations. A third neurotransmitter, called glutamate, supports your basic thought processes by keeping your brain in a fluid, alert state; this chemical also helps activate the limbic system. A fourth neurotransmitter chemical, called norepinephrine, responds to stress by triggering the ancient reflex to “fight or flight.”
How Drugs and Alcohol Alter Neuron Communication
All addictive substances make at least short-term alterations in the production of specific neurotransmitters that make neuron-to-neuron communication possible. Some of these alterations produce the primary effects of drug and/or alcohol use, which can include feelings such as intoxication, euphoria, or sedation. Other substance-related neurotransmitter alterations produce secondary physical changes such as reduced or accelerated breathing rates, or a reduced or accelerated heart rate.
The Importance of Dopamine
When it comes to the potential for substance addiction, the key neurotransmitter alteration is an increase in the presence of dopamine. In fact, on a chemical level it’s fair to say that, initially, most substance abusers keep using their substance of choice because they enjoy the pleasurable sensations triggered by higher dopamine supplies inside the limbic system. Among substances that work by activating this system, the increase in normal dopamine levels ranges anywhere from 200 percent to 1000 percent. With this type of reward, substance abusers have a strong chemical incentive to continue their actions.
Damaging Brain Changes
When a substance abuser keeps using for extended periods of time, his or her brain will make certain adjustments in an attempt to adapt to its new neurochemical reality. Inside the limbic system, dopamine production will drop or, alternatively, neurons in the system will become less sensitive to dopamine’s effects. Gradually, any given dose of a drug will have a smaller effect on dopamine levels, and will therefore produce smaller pleasurable rewards. Scientists refer to this phenomenon as drug tolerance. To offset the effects of tolerance, abusers commonly increase their average dosage of the substance in question. However, the effects of this compensation will only go so far and, in advanced cases of tolerance, abusers may drastically limit or essentially wreck their ability to feel pleasure from their substance of choice, or from any other source.
As stated previously, the neurotransmitter glutamate also plays a secondary role in normal limbic system activity, as well as a primary role in your ability to engage in conscious thought processes such as forming new memories, retaining old memories, making decisions, sustaining logical chains of thought and learning new skills or information. Over time, substance abuse-related changes in glutamate levels can degrade all of these functions and lead to long-term impairments in normal thought patterns. Glutamate-related changes also play a major role in the formation of uncontrollable drug cravings, as well as reflexive behaviors that support these cravings in both active and recovering addicts.
By the time a substance abuser experiences persistent drug cravings and reflexively responds to those cravings, he or she is firmly in the grips of an active addiction. Unfortunately, by this time he or she has also undergone widespread changes in normal brain function. This is why experts in the field typically refer to addiction as a brain disease. Even when a user stops drinking or taking drugs, damaging changes in the brain can linger for months or years, and it is this lingering damage that largely accounts for the common problem of relapse during drug and/or alcohol treatment. According to the National Institute on Drug Abuse, treatment programs and recovering addicts do best when they view addiction as a chronic condition and view relapse as a predictable, survivable bump in the road to long-term health and well-being.
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